SELECT type,email FROM lists,aliases WHERE lists.uid='user@example.com'; SELECT type,email FROM lists,aliases WHERE aliases.alias='user@example.com' and lists.uid=aliases.uid; The above MySQL queries return results almost instantly. The below query takes ages but it should just give the union of the results of both the above queries. How can I get the result of the above two queries with a single query that doesn't take ages? I guess that the problem is that it's looking up the aliases table for every row in the lists table. How can I stop it doing that? SELECT type,email FROM lists,aliases WHERE (lists.uid = 'user@example.com' or (lists.uid=aliases.uid and aliases.alias='user@example.com')); -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/